A control system to provide a controlled spin about an arbitrary axis is disclosed in U.S. Pat. No. 4,961,551, commonly assigned with the present application, such a control system frees a spinning spacecraft from the requirement to be mass balanced and to spin about a principal axis of maximum or minimum inertia. However, that disclosure does not address the process of capture initialization of the desired spin motion.
The spin axis capture of the present invention has, as one application, the transition from spin about a principal axis of inertia to spin about the thrust axis of the liquid apogee motor which is not aligned with the principle axis of inertia. In prior applications, the apogee motor thrust axis has either been aligned with the principal axis of inertia or, if not so aligned, the spacecraft is not spin stabilized. Rather, the spacecraft is three axis stabilized with full three axis attitude sensing and control. Such stabilization systems require higher band width control, larger torquers (thrusters, for example) and much more complex sensing and control implementations.